In recent years, light-emitting devices including semiconductor light-emitting elements (LEDs) having a small size, a long life, and low power consumption have been used for various lighting applications. In addition, light-emitting devices which emit white light by combining an LED and a fluorescent material, which absorbs the light from the LED, and can generate light having a long frequency therefrom by frequency conversion, have been widely developed and commercially produced. Such light-emitting devices which can emit white light are rapidly becoming commonplace as backlight sources in liquid crystal display (LCD) panels of flat-screen LCD televisions.
Such a use as a backlight source requires the light-emitting devices not only to achieve a small size and high brightness, but also to provide a broad light distribution characteristic so as to emit uniform white light in a broader range. Likewise, a similar need exists in the field of general lighting.
Conventionally, technologies for implementing a broad light distribution characteristic in a backlight source are disclosed in, for example, Patent Documents 1-3.
Patent Document 1 discloses a configuration in which a light direction-changing unit having a V-shaped center is provided over an LED, and light from the LED is reflected at an inner wall surface of the indentation, allowing the light to be output in transverse directions. Patent Document 1 discloses one example of the light distribution characteristic of such a configuration, which is as wide as approximately 140°.
As another measure to provide a broad light distribution characteristic, Patent Document 2 discloses a configuration of a light distribution lens having a particular shape. Patent Document 2 describes that this lens can achieve a light distribution characteristic of an angle greater than or equal to 170°. In addition, Patent Document 3 discloses a measure to achieve a broad light distribution characteristic by using a light-scattering material in addition to a lens. The configuration is such that an optical member having a similar shape to that of Patent Document 1 is provided over an LED, and a light-scattering layer containing a light-scattering material is formed on the V-shaped center of the optical member. The light-scattering layer scatters the light escaping from the LED to above the optical member, thereby increasing the light output component in transverse directions.